The invention concerns a device for preventing solid bodies from entering areas between two rotating machine parts, relative to each other.
Some types of machines such as electrically driven pumps and mixers are provided with one or several seals, usually mechanical seals, between the hydraulic unit and the driving unit. The seal prevents liquid from going along the driving shaft into the driving unit and cause damage in the latter.
A mechanical seal consists of two seal rings, one rotating and one non-rotating, which are pressed towards each other. The seal is lubricated and cooled by the surrounding medium and are exposed to severe strain, especially if the medium contains large amounts of solid bodies or pollutants. Because of the high pressure, these solid bodies may enter between the seal surfaces and cause damage, thus creating a leakage.
In order to provide the mechanical seal with as good an operating condition as possible, a pure liquid, water or even a gas may be brought to the seal area. The polluted liquid is then held back from the seal surfaces and the risk of damage decreases.
The described method has however certain disadvantages, in that the pure medium which is fed continuously costs money and may under certain circumstances cause harmful dilution of the surrounding medium.